Conventional marine bilge pumps typically have restricted downstream outlets that can be fitted with non-return valves. These pumps typically are prone to air-lock. To overcome this problem, it is known in the art to drill a small hole at the pump outlet, to thereby allow the air to escape. One such pump is disclosed in U.S. Pat. No. 3,707,344, which is incorporated herein by reference in entirety. U.S. Pat. No. 3,707,344 discloses a water pump such as for use with a commercial ice maker wherein the pump is normally submerged but the operation of which is controlled in response to a condition of the system independent of the water level at the pump, whereby air bubbles may form at the pump inlet due to a low level of water upon initiation of the pump operation. A breakup means is mounted on the impeller of the pump to project through the inlet to the pump for breaking up air bubbles that so form. The breakup means may comprise a pin member formed integrally with the impeller.
The following U.S. Patents disclose state of the art and are also incorporated herein by reference, in entirety:
U.S. Pat. No. 4,718,837 discloses a marine drive water pump impeller provided for a marine rotary vane positive displacement water pump. A filament wound annular drive hub is cured with resin polymer. A rubber annular base having a plurality of flexible radial vanes is molded in place around the drive hub. The resin polymer and the rubber are compatible and enable substantial bond strength there between. The hub is wound in the circumferential hoop direction, providing substantial hub strength.
U.S. Pat. No. 4,776,820 discloses a pump mechanism that is continuously operable by the engine of an outboard motor for discharging water that collects by seepage or leakage into the engine cowl. The pump mechanism includes an inlet conduit having an inlet end positioned closely adjacent to the bottom of an inclined channel formed in the lower section of the engine cowl, and an outlet conduit having an outlet end positioned exteriorly of the cowl.
U.S. Pat. No. 4,940,402 discloses in a rotary vane positive displacement pump, a pump impeller that has weights at the outer tips of the vanes of greater mass per unit volume than the vanes and increasing outward centrifugal force urging engagement of the outer tips against the pump housing sidewall.